In this paper we study a low frequency model for acoustic propagation in a 2D flow duct.For some Mach profile flow,we are able to give a well-posedness theorem.Its proof relies on a quasi-explicit expression of the so...In this paper we study a low frequency model for acoustic propagation in a 2D flow duct.For some Mach profile flow,we are able to give a well-posedness theorem.Its proof relies on a quasi-explicit expression of the solution which provides us an efficient numerical method.We give and comment numerical results for particular linear,tangent and quadratic profiles.Finally,we give a numerical validation of our asymptotic model.展开更多
嵌入式大气数据传感系统(Flush Air Data Sensing System,FADS)通过在飞行器表面特定区域布置测压孔测量来流压力,根据建立的气动模型反推得到飞行参数(攻角、侧滑角、马赫数、静压及动压等)。利用在尖楔前体表面三维区中分布测压孔的方...嵌入式大气数据传感系统(Flush Air Data Sensing System,FADS)通过在飞行器表面特定区域布置测压孔测量来流压力,根据建立的气动模型反推得到飞行参数(攻角、侧滑角、马赫数、静压及动压等)。利用在尖楔前体表面三维区中分布测压孔的方法,根据三维区中的流动特征和压力分布规律,建立压力分布与飞行参数之间的关系。试验结果表明,基于三维区理论的FADS系统得到的马赫数误差在5%左右,精度较高。展开更多
This paper presents the result and analysis of the composition of energy loss occurring in the hydro turbine.Two new types of energy losses,namely the hydraulic loss in the flow channel and the impact loss,are defined...This paper presents the result and analysis of the composition of energy loss occurring in the hydro turbine.Two new types of energy losses,namely the hydraulic loss in the flow channel and the impact loss,are defined.All losses within the hydro turbine are divided into four types and the loss coefficients are defined accordingly.Expressions or characteristic descriptions of these losses as well as the calibration method of the loss coefficients are presented.Furthermore,the torque model of the hydro turbine where the inner energy loss takes place is established.The developed model has been used to calculate the power loss due to the mechanical friction generated by the units’rotation to solve the difficulty of measurements of the mechanical friction loss in the hydro turbine.The definition of the impact loss explains the phenomenon that the loss of no-load is greater than that of the rated operation.A set of conversion coefficients are defined using the characteristic parameters at the rated operation,which are used to transform the parameters in the torque model into those that are easily measured.Therefore,the expression of the hydro turbine power is converted into a function that has the main servomotor displacement as its single variable.This makes the proposed model be convenient to use.Finally,the proposed model and methods are calibrated and verified using the measured data of a hydropower plant.Good agreement between the modeled results and the measurements indicates that the proposed model can represent the inner energy loss characteristics of the hydro turbine.展开更多
Based on the morphology of Luoshan-Hankou reach at the middle Yangtze River, the one-dimensional, unsteady flow and sediment transport numerical model was adopted to study the generalized cha nnel equilibrium profile...Based on the morphology of Luoshan-Hankou reach at the middle Yangtze River, the one-dimensional, unsteady flow and sediment transport numerical model was adopted to study the generalized cha nnel equilibrium profile. The variation of the longitudinal equilibrium profile, and the r elation with the condition of the inflow water and sediment from the upper reach were analyzed. Meanwhile, the numerical simulation results were compared with t he corresponding theoretical results. Finally, the equilibrium longitudinal slop e variations and its impact on flood control were analyzed after the sediment tr ansport process has changed.展开更多
文摘In this paper we study a low frequency model for acoustic propagation in a 2D flow duct.For some Mach profile flow,we are able to give a well-posedness theorem.Its proof relies on a quasi-explicit expression of the solution which provides us an efficient numerical method.We give and comment numerical results for particular linear,tangent and quadratic profiles.Finally,we give a numerical validation of our asymptotic model.
文摘嵌入式大气数据传感系统(Flush Air Data Sensing System,FADS)通过在飞行器表面特定区域布置测压孔测量来流压力,根据建立的气动模型反推得到飞行参数(攻角、侧滑角、马赫数、静压及动压等)。利用在尖楔前体表面三维区中分布测压孔的方法,根据三维区中的流动特征和压力分布规律,建立压力分布与飞行参数之间的关系。试验结果表明,基于三维区理论的FADS系统得到的马赫数误差在5%左右,精度较高。
基金supported by the National Natural Science Foundation of China(Grant Nos.50839003,50949037)the Natural Science Foundation of Yunnan Province(Grant No.2008GA027)partly by the Talent Training Foundation of Kunming University of Science and Technology(Grant No.KKZ3200906019)&University of Aberdeen
文摘This paper presents the result and analysis of the composition of energy loss occurring in the hydro turbine.Two new types of energy losses,namely the hydraulic loss in the flow channel and the impact loss,are defined.All losses within the hydro turbine are divided into four types and the loss coefficients are defined accordingly.Expressions or characteristic descriptions of these losses as well as the calibration method of the loss coefficients are presented.Furthermore,the torque model of the hydro turbine where the inner energy loss takes place is established.The developed model has been used to calculate the power loss due to the mechanical friction generated by the units’rotation to solve the difficulty of measurements of the mechanical friction loss in the hydro turbine.The definition of the impact loss explains the phenomenon that the loss of no-load is greater than that of the rated operation.A set of conversion coefficients are defined using the characteristic parameters at the rated operation,which are used to transform the parameters in the torque model into those that are easily measured.Therefore,the expression of the hydro turbine power is converted into a function that has the main servomotor displacement as its single variable.This makes the proposed model be convenient to use.Finally,the proposed model and methods are calibrated and verified using the measured data of a hydropower plant.Good agreement between the modeled results and the measurements indicates that the proposed model can represent the inner energy loss characteristics of the hydro turbine.
基金Project supported by the National Natural Science Foundation of China (Grant No:59890200) the Ministry of Water Resources of
文摘Based on the morphology of Luoshan-Hankou reach at the middle Yangtze River, the one-dimensional, unsteady flow and sediment transport numerical model was adopted to study the generalized cha nnel equilibrium profile. The variation of the longitudinal equilibrium profile, and the r elation with the condition of the inflow water and sediment from the upper reach were analyzed. Meanwhile, the numerical simulation results were compared with t he corresponding theoretical results. Finally, the equilibrium longitudinal slop e variations and its impact on flood control were analyzed after the sediment tr ansport process has changed.
